The Collaborative International Dictionary of English v.0.48:

Cadmean \Cad*me"an\ (k[a^]d*m[=e]"an), a. [L. Cadmeus, Gr.
   Kadmei^os, from Ka`dmos (L. Cadmus), which name perhaps means
   lit. a man from the East; cf. Heb. qedem east.]
   Of or pertaining to Cadmus, a fabulous prince of Thebes, who
   was said to have introduced into Greece the sixteen simple
   letters of the alphabet -- [alpha], [beta], [gamma], [delta],
   [epsilon], [iota], [kappa], [lambda], [mu], [nu], [omicron],
   [pi], [rho], [sigma], [tau], [upsilon]. These are called
   Cadmean letters.
   [1913 Webster]

   Cadmean victory, a victory that damages the victors as much
      as the vanquished; probably referring to the battle in
      which the soldiers who sprang from the dragon's teeth sown
      by Cadmus slew each other. Similar to a Pyhrric victory.
      [1913 Webster +PJC]